The Area of Application of Laval Nozzles in Flow-Rate Measurement Technique

Using examples of their use in standard and working instruments for measuring mass flow rate and a variety of gas volume flow rates, it is shown that critical nozzles and, particularly the Laval nozzle, can occupy an important place in the system of metrological facilities for this form of measurement.__________Translated from Izmeritel’naya Tekhnika, No. 4, pp. 48–52, April, 2005.     

Nonenzymatic Oligomerization of 3′,5′‐Cyclic CMP Induced by Proton and UV Irradiation Hints at a Nonfastidious Origin of RNA

We report that 3′,5′‐cyclic CMP undergoes nonenzymatic di‐ and trimerization at 20 °C under dry conditions upon proton or UV irradiation. The reaction involves stacking of the cyclic monomers and subsequent polymerization through serial transphosphorylations between the stacked monomers. Proton‐ and UV‐induced oligomerization of 3′,5′‐cyclic CMP demonstrates that pyrimidines—similar to purines—might also have taken part in the spontaneous generation of RNA under plausible prebiotic conditions as well as in an extraterrestrial context. The observed polymerization of naturally occurring 3′,5′‐cyclic nucleotides supports the possibility that the extant genetic nucleic acids might have originated by way of a straight Occamian path, starting from simple reactions between plausibly preactivated monomers.     

Possible Superconductivity in TiSe2 Intercalated by Transition Metals

Electric conductivity and magnetoresistence data for TiSe₂ intercalated by Fe²⁺ and Cr³⁺ are interpreted as superconducting state with T _c ∼ 5 and 4 K, respectively.     

Singularities of compressional wave propagation in hard rock masses

G. V. Plekhanov Mining Institute, Leningrad. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 60–64, May–June, 1988.     

Generation of traveling surface plasmon waves by free-electron impact

The injection of a beam of free 50 keV electrons into an unstructured gold surface creates a highly localized source of traveling surface plasmons with spectra centered below the surface plasmon resonance frequency. The plasmons were detected by a controlled decoupling into light with a grating at a distance from the excitation point. The dominant contribution to the plasmon generation appears to come from the recombination of d-band holes created by the electron beam excitation.